Title:

Macho (RIP):  Halo Dark Matter, Galactic Structure and the Time Domain



Kem Cook
Lawrence Livermore National Lab



Abstract:

In the last decade, a number of different projects have been mounted
to detect and follow the progress of gravitational microlensing by
compact objects, an extremely rare event.  These projects, driven by
the need to monitor millions of potential source stars, have opened
the time domain in wide-field astronomy.  One of the original
projects was the MACHO Project, a survey to determine whether there
is a significant baryonic component to the dark matter in the halo of
the Milky Way.

The MACHO Project collected 8 years and 7.3 Tbyte of data on 99
square degrees toward the Magellanic Clouds and the bulge of the
Milky Way.  Half square degree fields were sampled, simultaneously in
two bands, roughly every three days and light curves for about 55
million stars to a depth of about magnitude 21 have been collected in
a photometry database.  This database has been analyzed for
microlensing and about 500 events toward the Bulge and about two
dozen toward the Magellanic Clouds have been detected.  We have also
identified about 500,000 variable stars.  These have been analyzed
yielding new results in the astrophysics of pulsating stars, new
categories of stellar variability, and such disparate detections as
new high proper motion stars, new quasars and reddening maps of the
bulge.  The MACHO database and similar ones continue to provide
opportunities for new science as well as prototypes for next
generation databases generated by future large surveys. I will
present some of the recent results from MACHO as examples of
scientific investigations using a time-domain database as motivation
for future data mining activities.